Method and apparatus of eddy current monitoring for chemical mechanical polishing

Abstract

A polishing system can have a rotatable platen, a polishing pad secured to the platen, a carrier head to hold a substrate against the polishing pad, and an eddy current monitoring system including a coil or ferromagnetic body that extends at least partially through the polishing pad. A polishing pad can have a polishing layer and a coil or ferromagnetic body secured to the polishing layer. Recesses can be formed in a transparent window in the polishing pad.

What is claimed is: 
     
       1. A polishing pad, comprising:
 a polishing layer; 
 a transparent window in the polishing layer, wherein the window has a recess formed in a bottom surface thereof; and 
 a ferromagnetic body having an upper portion in the recess of the window and secured to the window with an adhesive and a lower portion below the bottom surface of the window, wherein a coil is wound around the ferromagnetic body. 
 
     
     
       2. The polishing pad of  claim 1 , wherein the window includes a plurality of recesses formed in a bottom surface thereof, and a plurality of ferromagnetic bodies are positioned into the recesses. 
     
     
       3. The polishing pad of  claim 1 , wherein the polishing pad further comprises a backing layer. 
     
     
       4. The polishing pad of  claim 1 , wherein a position of the ferromagnetic body relative to a surface of the polishing layer is adjustable. 
     
     
       5. The polishing pad of  claim 1 , wherein the ferromagnetic body is positioned with a longitudinal axis perpendicular to a surface of the polishing layer. 
     
     
       6. The polishing pad of  claim 1 , wherein the ferromagnetic body is positioned with a longitudinal axis at an angle greater than 0 and less than 90 degrees to a surface of the polishing layer. 
     
     
       7. The polishing pad of  claim 1 , wherein the ferromagnetic body is secured to the window with an epoxy. 
     
     
       8. The polishing pad of  claim 1 , wherein the window is a polymer. 
     
     
       9. The polishing pad of  claim 8 , wherein the transparent window has a top surface that is flush with a polishing surface of the polishing layer. 
     
     
       10. The polishing pad of  claim 1 , wherein the coil is positioned below the window. 
     
     
       11. The polishing pad of  claim 1 , wherein the ferromagnetic body projects below a bottom surface of the window. 
     
     
       12. The polishing pad of  claim 1 , wherein the ferromagnetic body is completely enclosed in the window. 
     
     
       13. The polishing pad of  claim 1 , wherein the body is a rod and the coil wraps around the body but is unattached to the body. 
     
     
       14. The polishing pad of  claim 13 , wherein the coil includes electrical connections configured to be coupled to contact pads. 
     
     
       15. The polishing pad of  claim 1 , wherein the body is a rod and the coil wraps around the body and is attached to the body. 
     
     
       16. The polishing pad of  claim 1 , wherein the body is a rod and the coil wraps around the body outside of the recess and epoxy surrounds the body in the recess. 
     
     
       17. The polishing pad of  claim 16 , wherein the rod is a cylinder. 
     
     
       18. The polishing pad of  claim 16 , wherein the rod is a trapezoid.